Installation guide to tunnel fire protection systems

Ceilings

Promat boards can be installed either directly to the concrete surface or mounted on a sub-frame or even on a suspended ceiling.

Promat offers the possibility of a system which attaches the fire protective boards directly to the concrete.

Lost Formwork System

This system is applied in new build immersed and cut&cover tunnels.

This is the easiest and most economical way of applying a fire protective layer to a concrete tunnel with a rectangular cross section.

The system consists of the following installation steps:

The PROMATECT® boards are laid on the load-bearing formwork, justbuttjointing one board next to the other

The first layer of reinforcement is installed

Stainless steel screws are partly inserted in the PROMATECT® boards

The concrete is poured

After the concrete is sufficiently cured the formwork will be extracted

Suspended ceilings

protective membrane

Especially (older) city tunnels which were built using a cut and cover method have been constructed by means of steel and/or concrete roof beams with a concrete slab or a composite steel/concrete slab on top of the beams. Quite frequently the space between the beams is utilised to install pipes, cable trays and other services. In case of a refurbishment of such a tunnel the protective membrane system is both technically and commercially the most feasible option.

The protective membrane system consists out of a steel frame which is suspended from the load bearing structure or, depending on the span of the ceiling, can be supported along the walls only.
The designer of the suspended steel frame has two options for the horizontal load bearing members:

1. the use of C, Z or omega profiles

2. the use of a trapezoidal steel decking,

Typically the design of such a suspended steel frame is conducted by a local structural engineer.
From below the PROMATECT®-T boards will be screwed to the suspended steel frame, either the profiles or the trapezoidal steel sheets.

Further technical information is available at the Promat technical department.

smoke extraction plenums

A common way of providing smoke extraction systems in tunnels is the construction of a smoke extraction plenum in the tunnel roof space, the so called transverse ventilation system. In case of an emergency the smoke and hot gasses will be extracted into the plenum through smoke inlets or hatches.

Such a plenum can either be constructed out of concrete or steel. Regardless of the selected construction method, the structural integrity of this plenum during fire is of utmost importance as the ventilation philosophy is depending on it. In case (part of) the plenum would collapse during the fire event, the intended smoke management approach would be lost, with all possible major implications as a result, let alone the hampering effect it would have on emergency response teams.

Such a smoke extraction plenum gets exposed to tunnel fire temperatures from both sides, e.i. from below but also from the top because the hot gasses are pulled into the duct. Especially at the location of the hatches the temperature exposure will be equally high from both sides.
Therefore, regardless of the selected construction method, such a plenum system requires thermal protection from both sides and not only from below.

In case the plenum is constructed out of concrete we refer to the section on this website detailing concrete protection.
The other option is to construct the plenum using a steel frame, which would span from wall to wall, with intermediate hanger rods if mechanically required. As described above, such a frame requires thermal protection from below and from the top. Also the hanger rods do require thermal protection in order to prevent that these would elongate due to thermal expansion, potentially causing unwanted deflection and sagging of the plenum.

The smoke extraction plenum system consists out of a load bearing steel frame, which can be made out of square hollow sections (SHS) or a trapezoidal steel decking.
The PROMATECT®-T boards will be screwed to either side of the steel frame, also covering the edges at the location of hatches.

Escape routes

Typically in circular tunnels the tunnel roof space can be utilised to create an escape route above the tunnel tube by means of constructing a suspended ceiling system. Because of the lack of space to provide a means of egress alongside the tunnel tube, this method is commonly used in this type of tunnels.

The escape route can be reached by the stairwell which connects to the tunnel tube at road deck level. The escape door leading to the stairwell should be fire proofed to prevent that the fire could spread into the escape route. Also the spread of smoke and toxic gasses into the escape route should be prevented. To achieve this, the escape route area is pressurised with fresh air, creating an overpressure to the surrounding atmosphere.

The area above the road deck can be used for escape route purposes only but can also be combined with a smoke extraction duct, in which case a fire rated wall separates the escape route area (fresh air) from the smoke extraction duct. This wall requires fire proofing because it will get exposed to tunnel fire temperatures through the hatches in the smoke extraction plenum system.

Such an escape route ceiling can either be constructed out of concrete or steel.
Regardless of the selected construction method, the structural integrity of this ceiling during fire is of utmost importance as this provides the most important means of egress in a fire emergency.

In case the escape route is constructed out of concrete we refer to the section on this website detailing concrete protection.
The other option is to construct it using a steel frame, which would span from wall to wall, with intermediate hanger rods if mechanically required. The separating wall can also be constructed such that it functions as a hanger rod. For obvious reasons, hanger rods should be avoided in the escape route area.

Apart from its structural integrity in case of fire an escape route ceiling has an additional thermal criterion being the maximum allowable temperature on the nonexposed face of the specimen, e.i. the temperature on the floor should not exceed a certain tenability level.

The French tunnel fire safety standard provides guidance to address this. The maximum allowable absolute temperature on the floor is set at 60ºC. This is not a temperature rise above ambient but an absolute maximum.

The escape route ceiling system is constructed using a trapezoidal steel sheet as the load bearing layer. From below, PROMATECT®-T boards are screwed to Z-profiles and are combined with high density mineral wool thus providing for the required thermal insulation of the system. On top of the trapezoidal steel decking a metal grid is foreseen to provide for a convenient surface to walk on.
The system as described above satisfies the thermal requirement of 60ºC on the floor surface as mentioned above.
An additional PROMATECT®-H board can be applied between the trapezoidal steel sheet and the metal grid to obtain even lower temperatures on the floor surface.

Walls

In Dutch immersed tunnels the ceiling is protected against fire using PROMATECT®-H boards. Also > 1m of the wall is protected with the same material. The heat of a fire rises to the ceiling and top side of the wall; that is where the damage will occur if no sufficient protection is foreseen.
In case of fire the exhaust duct of the Toulon tunnel will evacuate the smoke and hot gasses of the fire. These gasses will damage the surrounding concrete structure. In order to prevent this 30mm of PROMATECT®-T is applied to both the floor and wall structure.
On the other side of the wall is an escape route. To safeguard the escape route the temperature on the non-exposed side should be limited. The PROMATECT®-T creates sufficient insulation to obtain this.

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Ceiling and wall protection in tunnel
Caland tunnel in the Netherlands,
PROMATECT®-H ceiling and wall

During the full-scale fire tests in the Runehamar tunnel in Norway, one of the investigated items was the fire load on the wall. The conclusion was that the thermal exposure on the wall, measured at 1 meter above road level, was representative of a Hydrocarbon type temperature development. This means that the walls are exposed to temperatures in the range of 1000 - 1200ºC, in case of a fully developed tunnel fire (RWS type). As a result, the conclusion was drawn that the test results clearly show the necessity of a fire protective lining for wall applications.

curve radiation temerature on wall in tunnel

Cable ducts

In the event of a fire it is vital to the safety of the tunnel occupants that certain electrical systems remain functioning until people have escaped. Such systems will therefore require to be protected from fire for a specified period of time and include:

Lighting for means of egress (emergency escape route lighting) and areas of refuge

Exit signs

Communications

Electrically operated extinguishing systems

Electrically operated fire alarms

Ventilation systems (smoke extraction)

Tunnel drainage and fire pumps

Cable protection system constructed from PROMATECT®-H

In addition to protection from fire outside the duct, it is normally vital that any fire within the duct is contained e.g. if cable sheathing ignites due to an electrical overload. A suitably designed duct will:

Prevent the propagation of fire from one compartment to another

Assist in maintaining escape routes

Ensure the continuing operation of services

Reduce damage to localised areas

Contain smoke and toxic fumes from burning cables if the fire was caused within the cable enclosure

By enclosing standard cables in the Promat Cable Duct Systems, all the above requirements can be met, providing up to four hours fire protection, dependant on the duct construction, and the fire exposure curve, whilst avoiding the use of more expensive and bulkier fire-rated cables, which cannot provide a performance to the more extreme exposure curves, such as the HCM and RWS fire

Fire doors

Fire rated doors within tunnels are installed to provide a means of egress and to prevent the spread of fire, hot gasses and smoke from the tunnel to the surrounding compartments. Fire doors are installed:

At cross connections between two tunnel tubes

To provide access to an escape route (mid-tunnel-channel in an immersed tunnel)

To protect people who have fled into safe havens

In view of the smoke emissions from vehicles, and the high toxicity of this smoke as a result of the types of materials used in modern car manufacture, it is also imperative that any door will provide a high degree of resistance to the passage of smoke, and ideally, where used as access to safe havens, should provide a high degree of thermal insulation to reduce the affects of heat on the occupants of the chambers.

Any fire door situated within a tunnel should be capable of providing the same degree resistance to the aggressive and polluted environment as any other services.

In the design phase of a fire door it should be noted that the elongation of the steel members will cause gaps around the perimeter of the door, potentially introducing failure of the system. Apart from elongation the steel members will also tend to curve as a result of single sided heating.

A tunnel fire door should be fire tested in two configurations:

The door blade and hanging system inside the furnace

The door blade and hanging system outside the furnace

Promat has collaborated with a leading door manufacturer to produce a fire rated door applicable and suitable for tunnels and fire tested according to the RWS standard. For ease of operation in an emergency situation the door is designed as a sliding door which requires a minimum of force to open the door. The door provides thermal insulation for the full duration of 2 hours when exposed to the RWS fire development and remains its integrity as well. The material used to provide insulation to the door blade is PROMATECT®-T. The perimeter of the door blade, as well as some connections to the surrounding walls, are sealed by means of the intumescent PROMASEAL®-PL strips.

Penetration seals

In tunnels, various fire compartments are created. For example, escape routes and safe havens.
The walls, floors and ceilings of these compartments are penetrated by many technical services such as ventilation systems, cable trays and pipes.
Of course these “leaks” should be treated in a way to arrive at the same fire rating as the lining itself.

A penetration seal solution for electric cables

After the installation of the cables, this cable tray penetration needs to be sealed.

Joint systems

Tunnel structures exist out of concrete segments. The interconnecting joints are sealed with various sealing profiles, which is especially the case in water crossing tunnels. Obviously, these seals need to be protected from fire.
In the German Elb tunnel, Promat conducted special fire tests in order to prove the fire resistance of the PROMATECT®-H solution as shown below.

Joint protection in tubing elements in the Elb tunnel, Germany
Also in the case of an immersed tunnel building system, the complex joint structure needs to be safeguarded from fire. A lot of experience has been acquired in the Dutch tunnel building industry, while using PROMATECT®-H as a protective lining for both the concrete and the joints.

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